ACHIEVING A STABLE INELASTIC SEISMIC RESPONSE FOR MULTI-STORY CONCENTRICALLY BRACED STEEL FRAMES

摘要

When subjected to strong seismic ground motions, multistory concentrically braced steel frames are prone to a concentration of the inelastic demand along their height which results in large inter-story drifts that may lead to dynamic instability. This phenomenon is mainly attributed to the poor inelastic response of the bracing members combined to the inability of the framing system to redistribute vertically the inelastic deformations in the structure. Building height limitations have been recently introduced in the CSA-S16 Canadian Standard for the design of steel structures to minimize the risk of frame instability under strong ground motions. This paper briefly describes the phenomenon of dynamic instability in concentrically braced steel frames as well as the main parameters that influence this behavior. Solutions that have been developed to achieve a stable inelastic seismic response for multi-story braced steel frames are then presented and discussed.